Why radiator overflows

When the pressure exceeds the cap pressure rating, some fluid is allowed past the radiator cap and flows into the reservoir. Then, when the fluid cools and contracts at the end of the day, the cap allows the coolant in the reservoire to freely flow back into the engine, keeping the system full even after the fluid has contracted.

The level in the reservoir will rise and fall as the coolant heats up and cools down. If the reservoir is filled too full, excess will blow out the overflow tube when the coolant heats and expands. And put fresh fluid in there. Thank you everyone for your posts…The car is NOT over-heating at all, and the hoses are hooked up correctly to the reservoir tank.

I agree with your general consensus to change the radiator cap, perhaps the excess pressure is whats pushing all the coolant out of the reservoir.

Why Upgrade? This is a problem I personally experienced. The seal would degrade over time and seep coolant all over the exhaust heat shielding and sometimes the exhaust itself. A constant leak like this can lead to chronic overheating and potential damage to your engine components.

That plastic might look thick, but constant heating and cooling to these materials, not to mention the inevitability of staining from the colored coolant, are not kind to the tank. Make sure to check out our selection of aluminum expansion and overflow tanks for your vehicle! Thanks for Reading! Share this Article: Facebook Twitter Reddit. Expansion Tanks - OnAllCylinders. Expansion Tanks - Quietly Positive.

An inside look at the engineering of Mishimoto products. Write a Comment Email Required Name Required Website. Ben Davis February 9, Why is my coolant reservoir boiling and overflowing? Why is my coolant reservoir hot?

How do I reduce the pressure in my radiator? Can a bad thermostat cause pressure? How much pressure should a cooling system have? Due to this vacuum, a vacuum valve in the radiator cap opens allowing the coolant which was flown into the radiator coolant overflow tank back into the radiator. In older vehicles with no coolant overflow bottle, the air is sucked into the radiator instead of coolant which results in the formation of rust. So installing an overflow tank in your car is a good way to not only maintain the cooling system of your car but to save repairs and replacement expenses in the long run as well.

Great article. Thank you. Is the coolant overflow tank part of the whole cooling system pressurized system? That said, as coolant heats up it expands. Check your coolant level and if you notice the level decreasing, get that cap replaced asap. Probably not; air likes to collect at the highest point in the system, and this point will vary depending on the vehicle.

To properly bleed the system, the antifreeze level must be as high or higher than this point, which sometimes requires using a funnel in the radiator filler neck or the bleeder valve, if equipped. As the cooling system comes up to operating temperature, it pressurizes. The job of the overflow tank is to allow excess antifreeze to leave the cooling system once peak pressure is reached, and return once the pressure decreases again.

I have Hyundai sonata Y20 the radiator cap is missing and got overheated I replaced it with a new cap with pressure indicator of 0. Please what should be the correct radiator cap pressure to use for this car. Hi Mohammed, I am not sure if 0. Thank you so much I have replaced it with 1. Generally no. I am running an electric fan on the radiator and an electric fan on the ac condenser.

The radiator is a 4 row unit and cools well. If i put a recovery tank on the truck what cap pressure should I use? The radiator has a pressure release hose under the cap but there is no coolant overflow tank so when it gets hot the coolant just pukes onto the ground.